Truncated horn speaker having plurality of chambers



June \24, 1930. M. R. HUTCHISON TRUNCATED HORN SPEAKER HAVING PLURALI'IYOF CHAMBERS Filed May 24, 1927 v 3 Sheets-Sheet l INVENTOR. Mum

W 91. Aim

June 24, 1930. M. R. HUTCHIS ON 1,767,579

TRUNCATED HORN SPEAKER- HAVING PLURALITY OF CHAMBERS Filed May 24, 19273 Sheets-Sheet 2 I KAIEIZL fiZTOR 4 ATT RNEY.

Jime 24, 1930. M, R, HUTCHISON 1,767,679

TRUNCATED HORN SPEAKER HAVING PLUHALITY OF CHAMBERS Filed May 24, 1927 sSheets-Sheet 5 MM W ATTORNEY.

A Patented June 24, 1930 UNITED {STATES PATENT! OFFICE MILLER REESEHUTCHISON, OF WEST ORANGE, NEW JERSEY, ASSIQNOB, BY HESNE ASSIGNMENTS,1'0 ACOUSTIC PRODUCTS COMPANY, 01' NEW YORK, N.-Y., A COB- PORATION OIDELAWARE TRUNCATED 'KOBN SPEAKER HAVING PLURATJTY OF CKAMBBBBApplication fled Kay),

This invention relates to sound propagatin devices of the type in whicha mechanical diaphragm is utilized for imparting vibrations to a fluidmedium.

A dia hragm of a sound reproducing device sucr as a telephone receiveror a socallcd loud speaker, acts as a piston for producing compressionsand rarefactions of a column of air enclosed within the horn or withinthe receiver. The action of the diaphragm is opposed by the friction andinert1a of the diaphragm itself and by the pressure of the air column.The horn may correspond to an open end pipe which has the characteristicof bein resonant to an air wave having a length ouble that of the pipe.If the diaphra 'm vibrates at this resonant frequency of the horn, thevibrations thereof will be in phase with the vibrations which are set upin the air column, and, consequently, less resistance will be exertedupon the diaphragm than will be the case if the vibrations in thatelement and the air column were not in synchronism.

This invention provides a sound pro agating device having a new andefiicient iaphragm for imparting vibrations to an air column, and inwhich the friction of the air column is reduced to a minimum. Thereflection of the pro agated waves back onto the diaphragm is argelyprevented b the provision of an air space of constant y increasing crosssection from the diaphragm to the open end of the receiver or horn.

The above desirable features are accomplishcd in the present inventionby producing waves comprising rarefactions and compressions in adisk-shaped air 5 ace, the thickness of which increases from t 1e centertoward the periphery. At the center where the movement of the diaphragmis greatest the highest pressure is exerted and as the wave which isproduced travels outwardly in concentric circles the cross section ofthe air space constantly increases. At the outer periphery of the diskthe waves ma be defiected at right angles and applie to an annular aircolumn of constantl increasing cross section forming a horn. T einvention provides for the continuous progression of 1927; Serial in.193,514.

the produced waves from thecenter of the diap ra m to the outwardextremity of the horn an thereby lar 1y prevents the reflection againstthe diap ragm as well as eliminating all inert air space which wouldpro-' duce a damping effect upon the diaphragm. The outer annular airspace may be divided into a plurality of columns of different lengths,each of the columns being resonant to a wave of different frequenc suchas a note of the chromatic scale. ith such an arrangement the variousnotes of the chromatic scale may be reproduced.

The invention also consists in certain new and original features ofconstruction and combinations of parts hereinafter set forth andeiaimed.

. Althou h the novel features which are believed to e characteristic ofthis invention will be specifically pointed out in the claims appendehereto, the invention itself, as to its objects and advantages, the modeof its operation and the manner of its or anizatron, ma be betterunderstood by referring to the fo lowing description taken in connectionwith the accom anying drawing forming a part thereof, 1n which likereference characters have been used to denote like parts in the variousfigures. Since such illustration is, however, primarily for purposes ofdisclosure, it will be understood that the structure and the method ofoperation thereof may be modified in various respects without departingfrom the broad spirit and scope of the invention.

One embodiment of the invention has been shown for purposes ofillustration in the accompanying drawing, in which Fig. 1 is a frontelevation of a sound propagating device constructed in accordance withthis invention;

Fig. 2 is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is an end elevation of the device provided with resonatingsections of different lengths;

Fig. 4 is a section taken on the line 4-4 of Fig. 3;

Fig. 5 is an elevation partly broken away showing the invention appliedto a multihorn pancake type loud speaker; and

Fig. 6 is a section on the line 6-6 of and in particular to Figs. 1 and2, a-

cup shaped diaphragm 1 is peripherally mounted on casing 3, and isactuated b an electromagnetic unit 2, which ma be 0 an desired type,such as for exam e, the wel known push-pull ty in whic a force iscontinuously applie to the armature durin movement in both directions.The movabTe armature may be rigidly connected to diaphragm 1, byconnecting link 4 for the cur se of imparting vibrations thereto. iDiSlES having a slightl cone sha ed cross section is located para lel to anslightly spaced from diaphragm 1 and provides in connection with saidiaphragm, a disk-like air space of cross section increasing toward theperiphery thereof, and of minimum cross section at the point at whichthe vibrations of diaphragm 1 are of greatest amplitude. Y

Diaphragm 1 may be extended to form a slightly tapered cylindricalmember 7 terminating in a bell 10. The edges of disk 5 may also beextended to form a tapered c lindrical member 8 which is flaredoppositely to member 7, and provides in connection therewith an annularair space of continuously increasing cross section. Cylinder 8 may beprovided with a hell 9 similar in shape to hell 10 which is formed uponmemher 7, said bells forming the opening of the annular air spacethrough which waves are to be propagated. Supportin members 11 may beemployed for rigidTy holding members 7 and 8 in spaced relationshi 1 hconsidering the operation of Fig. 1, when the dia hragm 1 is forcedtoward disk 5, the air or other gaseous medium therebetween will becompressed, the greatest compression occurring at the center of thediaphragm, at which point link 4 is attached, and at which point thethickness of the disk of air between the diaphragm and disk 5 is theleast. The compression thereby introduced into the air disk will bepropagated outwardly in circles of progressively increasing diameteruntil the edge of the disk and the cup-shaped diaphragm is reached. Atthis point the concentric circles will be deflected in a directionsubstantially at right angles and will be propagated out through thehorn shaped annular space between cylinders 7 and 8. Said cylindersshould be so shaped that the cross section of the annular air 5 ace willincrease by an amount such that t a friction of said cylinders on themoving air column will be reduced to a minimum. Furthermore, the openingbetween bells 9 and 10 should be such that waves ma be transferred tothe surrounding atmosp ere most efiiciently.

Referring to Figs. 3 and 4, the various elements described 1n connectionwith Fig. 1 are represented by similar reference numerals, and co uentlywill not be described in detail. In igs. 3 and 4, however, members 7 and8 have been shown as extended at a considerable angle to a line normalto the diaphragm, member 8 in effect being cone shafiled and terminatingin an apex 14.

e annular space between said members 7 and 8 has been dividedlongitudinally by fins '12 in the manner shown in Fig. 3 where- .by aplurality of se arate air columns are produced through w ich the airwaves are independently propagated. The entire assembly has been shownas truncated, the end thereof terminating in a line 13. This arrangementallows each of the air columns to be of a different length whereby theymay resonate at different frequencies. Obviouslfy, the line 13 may takeany desired form or imparting the required characteristics ,to thevarious air columns. It has been shown as a straight line by way ofillustration only. In order to accurately reproduce musical notes, theannular air space may be divided into 12 columns and the len h of eachcolumn may be such that it wi l resonate to a particular note of thechromatic scale. As shownin Fig. 3 24 columns may be employed andarranged so that two columns resonate to each of the notes of the scale.

In the operation of a device constructed as above, a sound wave, afterbeing reflected from the cup shaped periphery of the diaphragm 1, willbe impressed u on each of the various air columns into w ich the annularspace between members 7 and 8 have been divided. The wave will, however,impart the greatest vibrations to the air column which is resonant tothe fre uency of the wave, and will be re-enforce by said air column andpropagated into the surrounding space thereby. The vibrations offrequencies other than those present in the chromatic scale will notfind a resonant air column and consequently will not be amplified. Theinvention, therefore, provides not only forthe selective amplificationof the various musical notes but effectively suppresses notes of otherfrequencies, such as for example, those produced by static.

In the modification-shown in Fi 5 and 6, the invention is shown.as apied to a pancake type speaker-in which t e air column between disks 20and 21 is divided by a plurality of spirally extending members 22 intovarious spiral air columns of different 7 lengths and resonant todifferent frequencies. The diaphra m 1 and the disk 5 cooperatingtherewit together with the vanous actuating elements are similar tothose disclosed in Fig. 1 and are given similar reference numerals.

In the operation of this device, the air waves after increasing indiameter until the periphery of diaphragm 1 is reached are refiectedinto thevarious spiral air columns through which they are impressed uponthe surrounding medium. Each air column then selects and amplifies thewave to which it resonates.

By the present invention, a sound propagating device is produced inwhich the reflection in-the various air columns and the friction in. thediaphragm is materially reduced. The diaphragm is allowed to act aspiston for producing rarefactions and compressions on the medium actedupon, such as air, but the force required to move the diaphra is reducedto a minimum by reason of t e continuously increasing cross section ofthe air column in which the vibrations are set up. Bv providing aplurality of air columns, eac resonatin at a frequency corresponding toa note in the chromatic scale, the accurate reproduction of musicalnotes is assured with a consequent elimination of undesired notes oflower frequencies, or of f uencies which are not multiples of one of t enotes of said scale.

A reproducing unit constructed in accordance herewith is capable ofaccurately reproducing all musical notes and of preserving the-tonalqualities thereof but serves to su press all notes of other frequencies.T e reproduction is es ecially efiiclent by reason of the reducedfriction throughout the air column.

While certain novel features of the invention' have been shown anddescribed and are pointed out in the annexed claims, it will beunderstood that various omissions, substitutions and changes in theforms and details of the device illustrated and in its olperation may bemade by those skilled in t e art without departing from the spirit ofthe invention.

What is claimed is:

' 1. A sound pro agating device comprising a substantially at diaphragmand a cone shaped disk s aced therefrom to form a substantially disshaped space having a eater cross section at the periphery thereof't anat the center.

' said diaphragm to form in connection therewith a disk like air spaceof increasing crosssection, said diaphragm and said member belar spaceof increasing cross section and a plurality of longitudinally extendingmemers for dividing said annular air space into a plurality of separateair columns, each of said air columns being of a suitable length toresonate to a note corresponding to a particular frequency in thechromatic scale.

3. A sound reproducing device comprising a diaphragm means for impartingvibrations thereto, a member co-operating with said dia hragm to form inconnection therewith a disk like air space having a cross sectionincreasing toward the periphery, said diaphragm and said member beingextended and flared to produce an annular space of increasing crosssection, and a. plurality of Ion itudinally extending members dividingsaid annular air space into a plurality of separate air columns, each ofsaid air columns being resonant to notes of a definite frequency.

4. A sound reproducing device comprising a diaphragm, means forimparting vibrations thereto, a member co-operating with said diaphragmto form in connection there with a disk like air space of cross sectionin creasing toward the periphery( said diaphragm and said mem er beingextended at substantially right angles and flared ,to produce an annularspace of increasing cross section, and a plurality of longitudinallyextending-members for dividing said annular air space into a pluralityof separate air columns, each of said air columns being resonant towaves of a different frequency.

5. A sound reproducing device com rising a cup shaped diaphragmperipheral y supported, means for vibrating the center portion thereof,a member co-operating with said diaphragm to form in connectiontherewith a disk llke air space of cross section increasing toward theperiphery, said dial vphragrn and said member being extended atsubstantially right angles and flared to produce an annular space ofincreasing cross section, a plurality of longitudinally extendingmembers for dividing said annular air space into a lurality of separateair columns, each 0 said air columns being of a suitable len h toresonate to a note having a particular reg uencgto the chromatic scale.

Signed at ork, in the county of New York and State of New Yorkthis 20day of May, A. D. 1927.

MILLER REESE HUTCHISON.

ing extended and flared to produce an annu-

